Device for straightening circular cross section workpieces having varying diameters



n. GROPPINI 3,492,850 DEVICE FOR STRAIGHTENING CIRCULAR CROSS SECTION Feb. 3, 1970 WORKPIEGES HAVING 'VARYING DIAMETERS 2 Sheets-Sheet 1 Filed Feb. 21, 1968 FIG] INVENTOR. v FIE. 1/5 mseo GROPPINI ATTORNEYS Feb. 3, 1970 D. GROPPHNI 3,492,859

DEVICE FOR STRAIGHTENING CIRCULAR CROSS SECTION WORKPIECES HAVING VARYING DIAMETERS 7 Filed Feb. 21, 1968 2 Sheets-Sheet 2 DIEGO GROPPINI United States Patent 3,492,850 DEVICE FOR STRAIGHTENING CIRCULAR CROSS SECTION WORKPIECES HAVING VARYING DIAMETERS Diego Groppini, Dalmine, Italy, assignor to Dalmine S.p.A., Milan, Italy, an Italian corporation Continuation-impart of application Ser. No. 440,886, Mar. 18, 1965. This application Feb. 21, 1968, Ser.

No. 707,109 Claims priority, application Italy, Mar. 24, 1964, 45,382/ 64 Int. Cl. B21b 19/04; B21d 3/04 US. Cl. 72-98 7 Claims ABSTRACT OF THE DISCLOSURE The present application is a continuation-in-part of application Ser. No. 440,886 filed Mar. 18, 1965, and now abandoned.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a device for straightening circular cross section workpieces of varying diameters along their lengths.

Prior art Roller type devices are generally known for straightening cylindrical workpieces, usually in the form of bars and tubes. These known devices usually impart a combined rotary and translatory motion, i.e. a helicoidal motion to the workpiece, through the combined action of a plurality of driving and idle rollers, the axes of which are suitably inclined with respect to the axis of each workpiece to be straightened.

The assembly of rollers, besides impressing a continuous helicoidal motion to the workpiece due to their relative position with respect to the workpiece (which is usually opposed, alternated, staggered, etc.) also effects a continuous deflection or bending of the workpiece in all directions, and as the workpiece goes forward, this deflection extends throughout the length of the workpiece and overcomes its yield strength to straighten same.

In these known straightening machines, a suitable inclination of the driving and idle roller axes relative to the axis of the workpiece is performed as a function of the outer diameter of the latter. Depending on the deformation or bending rate to be eliminated, and on the thickness and physical characteristics of the workpiece, suitable thrusts or pressures are impressed on said bar through rollers which are able to provoke the required deflections in all directions and throughout the length of the workpiece.

In the conventional straightening machines, the rollers, after having been positioned in the correct position, are locked and retained in this position until all workpieces of the same stock are straightened. When other workpieces of a different diameter are to be straightened, the working position of the rollers must be adjusted when the machine is not in operation. Therefore, for each position of the rollers, they can only straighten cylindrical workpieces having the same diameter throughout their length.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a roller straightening device adapted to straighten workpieces having a circular cross section throughout their length, but having diameters which increase or decrease in any range. These workpieces may be hollow or solid, may be frusto conical in shape, or partially frusto conical and partially cylindrical, etc. Furthermore, they may be in the form of tapered poles formed by several members of an increasing or decreasing diameter.

The straightening rollers of the present invention are mounted in means which are of the irreversible type, i.e. adapted to maintain a fixed position regardless of the load impressed upon them and to controllably move in response to variation in diameter of the bar.

Briefly summarized, the device of the present inven tion is characterized by the use of a set of straightening rollers and a set of driving rollers which are suitably arranged with their axes inclined relative to the axis of the workpiece to be straightened. The driving rollers rotate the workpiece and impart an axial movement thereto by cooperating with the periphery of the workpiece, and at least a portion of the straightening rollers are adapted to move relative to the axis of the workpiece during the movement of the latter in response to variation in diameter of the bar.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be disclosed in the following description by making reference to the accompanying drawings in which:

FIG. 1 is an elevational view of the device according to the invention;

FIG. 1A is a bottom view of the device showing the relative positioning of the rollers;

FIGS. 2 and 3 are elevational views, partially in section, of two different mechanical driving systems; and

FIG. 4 is an elevational view, partially in section, of a device for varying the inclination of the axis of the roller with respect to the axis of the workpiece.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring specifically to FIG. 1 of the drawings, a pair of rollers A and A are disposed on one side of a workpiece H having an axis WW, and three rollers B B and B are disposed on the opposite side of the workpiece, it being understood that the number of these rollers may vary as necessary. Rollers B B and B are rotatably mounted in forks C C and C for rotation about their axes Z to Z the forks being pivotally connected to supports F F and F which in turn, are connected to the free ends of the piston rods of pistons N N and N respectively.

Three cylinders M M and M drive pistons N N and N to effect the radial displacement of the rollers B B and B respectively, relative to the workpiece H to insure the continuous contact of the latter rollers with the workpiece as the diameter of the latter varies.

Rollers A and A may be either fixed or movable in a radial dirction with respect to the workpiece, an apparatus for effecting the latter movement being shown in FIG. 1. Specifically, these rollers are rotatably mounted in forks C and C to rotate about their axes x and x the latter forks being pivotally connected to supports F and E, which are connected to the free ends of the piston rods associated with pistons N and N of cylinders M and M respectively.

By virtue of the pivotal mounting of each fork C -C with respect to their corresponding supports F F each roller A -A B -B B can oscillate about its respective axis t t y y and 3 so that its surface maintains contact with the surface of workpiece H to be straightened, independently of the different tapers and varying diameters of the workpiece within a definite range.

Referring to the specific arrangement of the rollers, the basic straightening device consists of rollers A and A on one side of the workpiece, and roller B on the opposite side thereof and intermediate with respect to rollers B and B Rollers B and B are utilized exclusively as drive rollers, i.e., they are driven by external means, not shown, to effect rotary and axial movement of the workpiece in cooperation, of course, with rollers A and A Therefore, it is the above-mentioned radial movement of the straightening rollers A A and B relative to the workpiece which is essential, this movement, of course, being effected by the cylinder-piston devices shown. For example, rollers A and A may be fixed while roller B is movable. Also, roller B may be fixed while rollers A and A are movable, or rollers A A and B all may be movable.

It is emphasized that this radial movement of any or all of the straightening rollers is such that the rollers are rigidly fixed in their new radial position with respect to the workpiece by means of the hydraulic cylinder-piston means shown, the rollers, of course, being free to pivot about axes t t y 3 and y It is to be understood that the control of the hydraulic cylinder-piston means is effected by automatic means not shown, which senses the variation in the diameter of the workpiece and effects a corresponding change in the hydraulic pressure acting on the respective pistons, during the rotation and translation of the workpiece.

Although the drive rollers B and B are shown as being radially movable by means of a hydraulic cylinderpiston device similar to those used in conjunction with the straightening roller, it is to be understood that these rollers may be mounted in any known manner, such as by elastic means, or the like, since they do not develop any straightening forces on the workpiece.

FIGS. 2 and 3 depict alternate embodiments of the apparatus to effect the radial movement of straightening rollers A A and B (and drive rollers B and B if desired), relative to the wokpiece H.

In particular, FIG. 2 illustrates the use of a radial cam P which may be rotatably driven about the axis of shaft P by any known means. Cam P acts on the extremity of a bar Q secured to the support F of a roller B, and is axially guided by supports Q Since cam P is eccentric with respect to axis P rotation of the cam will cause a corresponding movement of the roller B in a radial direction.

According to another embodimenL a roller B" may be moved in a radial direction by means of a screw R as shown in FIG. 3. This screw cooperates with a nut screw R secured to support F" of roller B" and is guided in an axial direction in support R The nut screw R is supported by supports S and is adapted to rotate about the axis of screw R by a drive motor (not shown) by means of a helical wheel and worm screw T.

The operation of the apparatus will be described with reference to :FIG. 1. The workpiece H is positioned adjacent the path between the rollers A A and B B and B and drive rollers B and B are moved into their proper radial position in contact with the workpiece by any known means such as by the hydraulic cylinder-piston as shown, or by elastic means, or the like. Rollers B and B are rotatably driven to rotate and axially move the workpiece between the rollers and the automatic sensing means senses the diameter of the workpiece, and actuates the hydraulic cylinder-pistons, or the like, associated with the straightening rollers A A and B to move the latter, or any combination thereof, into engagement with the workpiece.

The rollers A A and B due to the rotation of their respective supports about axes G G and K assume for each given diameter of the workpiece a suitable inclination to the axis WW of the workpiece to insure the maximum surface contact, and to apply the forces required to deflect the workpiece with respect to its axis WW as much as necessary. Due to the rotation and axial movement of the workpiece effected by drive rollers B and B the workpiece is subjected to said deflection in all directions, thereby causing a straightening of the workpiece throughout its length.

Since the workpieces can have cylindrical lengths and conical lengths with a different taper, the fact that the rollers together with their supports can pivot about axes t t y y; and y insures that the rollers engage the workpiece both in its cylindrical lengths and its conical lengths with different tapers.

Also, the arrangement is such that the angle between the axis of each of said straightening rollers and the axis of the workpiece defined by the projection of said two axes on a plane orthogonal to the line of least distance between said two axes, continuously varies as the outer diameter of the workpiece with which the roller is in contact varies. In other words, a continuous variation of the angle of inclination of the axes of the rollers with respect to the axis of the workpiece in plan view, or looking downwardly from a position over the workpiece and roller, is achieved. This may be effected by allowing the pistons associated with the rollers to freely rotate with respect to their corresponding cylinders, or by freely mounting the supports F on their corresponding piston rods.

This latter movement presents to the workpiece the largest Zone of support so as to reduce the specific load and eliminate any possibility of the rollers grooving or marking the workpiece, especially if it is of a tubular thin-walled type.

In the straightening process, the rollers move toward or away from the axis W--W of the workpiece along the axes which intersect centers G K and G K and through the axis of the workpiece (for roller B shifting occurs along an axis which intersects K and which is parallel to the shifting directions of the other rollers). The axes of rotation of the rollers (X and Z) as projetced on the plane of FIG. 1 are parallel to the generatrix of the workpiece with which the rollers are in con tact at their midsection (i.e. at a point on the line joining centers G /K and Gz/Kg).

The axes of rotation of the rollers (X and Z) in their projection according to a plane intersecting the axis of the workpiece, perpendicular to the plane of FIG. 1, are inclined with respect to the axis of the workpiece WW by angles which are dependent upon the diameter of the tube at the point of contact with the workpiece itself (see FIG. 1A). In particular, for rollers B B and B angle a is greater than a which in turn is greater than 04 Similarly, for rollers A and A angle [3 is greater than angle 5 Provision may be made for imparting a rotation of the respective supports F associated with the rollers about the axis of their corresponding piston rods as shown in FIG. 1, directly in response to the radial movement of the rollers with respect to the workpiece. A device for effecting this is shown in FIG. 4. As shown, the piston rod U of drive piston N' has a helical projection which cooperates with a helical groove in a sleeve V secured to cylinder M'.

Thus, with each axial movement of rod U, a rotation of the rod about its own axis takes place and therefore, a variation of the angle of inclination of the axis of roller B with respect to the axis of the workpiece, in a plan view is achieved, as a direct function of the radial distance of the roller from the axis of the workpiece, which of course, is a function of the diameter of the workpiece at its contact point with the roller.

In known machines on which workpieces having a constant diameter are straightened, the drive rollersmay be rotated with the same number of revolutions. However, in the present invention, since drive rollers B and B may, at any given time, be in engagement with diameters of a varying size, such as in the case when one of the drive rollers engages a cylindrical portion of the workpiece and the other, a conical portion, number of revolutions which said drive rollers must rotate to avoid sliding on the workpiece, must be adjusted continuously. This may be achieved by means of a kinematic differential mechanism inserted on the drive of the two driving rollers, if the latter are operated by a single motor or by means of an electrical differential, if operated by separate motors.

In this manner, the correct kinematic condition of entrainment or rollers B and B in engagement with such a workpiece is insured, and therefore, a suitable helicoidal motion will be imparted to the workpiece.

Of course, other variations of the specific construction and arrangement of this type device herein disclosed can be made by those skilled in the art without departing from the invention as defined in the appended claims.

I claim:

1. A device for straightening conical, tapered or stepped workpieces, comprising a plurality of straightening rollers engaging the periphery of a workpiece at approximately opposite sides thereof, means to rotate and axially translate said workpiece along a path between said straightening rollers to straighten said workpiece, and means unresiliently mounting at least one of said straightening rollers for individual driven movement in a radial direction with respect to said workpiece in response to variations in the diameter of the workpiece during move ment thereof, said mounting means including means whereby said radial movement is combined with a driven rotation of said rollers about the axes of their respective mounting means to vary the angle of inclination of said rollers with respect to the workpiece.

2. A device as set forth in claim 1 further comprising additional means mounting said straightening rollers for a free pivotal movement about an axis perpendicular both to the axis of the roller and to the axis of the respective mounting means.

3. A device as set forth in claim 1 wherein said means to rotate and axially translate said workpiece comprises at least one drive roller adapted to engage said workpiece.

4. A device as set forth in claim 1 wherein said mounting means comprises a hydraulic system.

5. A device as set forth in claim 1 wherein said mounting means comprises a cam arrangement.

6. A device as set forth in claim 1 wherein said mounting means comprises a screw-nut assembly.

7. A device as set forth in claim 1 wherein each of said rollers has a concave profile.

References Cited UNITED STATES PATENTS 2,016,038 10/1935 Hartley 7298 2,034,132 3/1936 Diescher 7298 2,049,992 8/1936 Brock 7298 2,189,609 2/1940 Lessman 72164 X 2,517,344 8/19'50 Picton 72162 X 2,556,120 6/1951 Sutton 7298 2,730,158 1/1956 Heintz 7298 3,187,536 6/1965 Zolton 7299 MILTON S. MEHR, Primary Examiner US. Cl. X.R. 

